function disableSelection(target){
if (typeof target.onselectstart!="undefined")
target.onselectstart=function(){return false}
else if (typeof target.style.MozUserSelect!="undefined")
target.style.MozUserSelect="none"
else
target.onmousedown=function(){return false}
target.style.cursor = "default"
}
//Sample usages
//disableSelection(document.body)
//disableSelection(document.getElementById("mydiv"))
